The body includes various passageways including blood vessels such as arteries, and other body lumens. These passageways sometimes become occluded or weakened. For example, they can be occluded by a tumor, restricted by plaque, or weakened by an aneurysm. When this occurs, the passageway can be reopened or reinforced, or even replaced, with a medical endoprosthesis. An endoprosthesis is an artificial implant that is typically placed in a passageway or lumen in the body. Many endoprostheses are tubular members, examples of which include stents, stent-grafts, and covered stents.
Many endoprostheses can be delivered inside the body by a catheter. Typically the catheter supports a reduced-size or compacted form of the endoprosthesis as it is transported to a desired site in the body, for example, the site of weakening or occlusion in a body lumen. Upon reaching the desired site, the endoprosthesis is installed so that it can contact the walls of the lumen.
One method of installation involves expanding the endoprosthesis. The expansion mechanism used to install the endoprosthesis may include forcing it to expand radially. For example, the expansion can be achieved with a catheter that carries a balloon in conjunction with a balloon-expandable endoprosthesis reduced in size relative to its final form in the body. The balloon is inflated to deform and/or expand the endoprosthesis in order to fix it at a predetermined position in contact with the lumen wall. The balloon can then be deflated, and the catheter withdrawn.
Body lumens often include bifurcated regions with branching pathways. Treatments, such as angioplasty and stent delivery, are sometimes required at locations proximate the branching physiology. A balloon configured for use with a bifurcated endoprosthesis can have a non-linear portion that expands the bifurcated portion of the endoprosthesis. It is desirable that upon deflation, the balloon forms a predictable low profile configuration that facilitates withdrawal from the body and is not likely to become caught on the endoprosthesis during removal.